In constructing a system for utilizing solar energy, it is highly advantageous to provide a solar reflector that can concentrate the solar energy and aim that concentrated energy at a specific target. This results in a more efficient system and can reduce the size and cost of the overall system.
While various solar reflectors, and reflectors of other electro-magnetic radiation, have been known in the art, they have tended to be heavy and expensive to make. In addition, many of these devices have complicated or impercise mechanisms for varying the focal length of the reflector. Typical prior art devices are disclosed in U.S. Pat. Nos. 2,952,189 to Pajes, 3,514,776 to Mulready, 4,033,676 to Brantley, Jr. et al, 4,046,462 to Fletcher et al, and 4,179,193 to Gillette et al. In addition, a variable focal length reflector is disclosed in the article entitled "Variable Focal Length Mirrors", Review of Scientific Instruments, Vol. 32, No. 2, February, 1961, pp. 210-211, by J. C. Muirhead.
Another curved reflector with a flexible membrane to adjust its focal length is disclosed in U.S. Pat. application Ser. No. 149,587, entitled "Curved Reflector With Adjustable Focal Length" by Johnson and Peckham, filed May 14, 1980, now U.S. Pat. No. 4,288,146, issued on Sept. 8, 1981. This reflector controls the depth of membrane deflection by a valve. The valve comprises an aperture in the membrane and a flowrestricting surface overlying the aperture and positioned in the housing at a depth equal to that of the desired deflection of the membrane. This arrangement is disadvantageous in that the valve is located on the reflective surface side of the membrane making access thereto difficult and adversely affecting the reflective characteristics of the membrane. Moreover, the use of a perforated membrane permits contaminants, such as water and airborne particulate matter, to enter the reflector and adversely affect its operation.